The SEER Program was initiated in 1972 in response to requirements of the National Cancer Program for assessing the magnitude of the cancer burden in the United States, and for identifying factors related to cancer risk and/or patient survival. The SEER Program has among its objectives: 1. To assemble and report, on a periodic basis, estimates of cancer incidence, especially among the following key cancer sites: breast cancer, lung cancer, colorectal cancer, prostate cancer, pancreatic cancer, and urinary bladder cancer. 2. To monitor annual cancer incidence trends to identify unusual changes in specific forms of cancer occurring in population subgroups defined by geographic, demographic, and social characteristics. 3. To provide continuing information on changes over time in extent of disease at diagnosis, trends in therapy, and changes in cancer patient survival. 4. To identify the occurrence of possible iatrogenic cancers, i.e., cancers that are caused by cancer therapy. 5. To serve as a research resource to the National Cancer Institute, and conduct studies dealing with current cancer control issues as well as problems related to the operation of the SEER Program.